Fair Value Measurements (Narrative) (Detail) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative, Gain (Loss) on Derivative, Net		$ (585)	$ (330)	$ 87
Guaranteed Minimum Income Benefit
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative, Gain (Loss) on Derivative, Net	[1]	(4)	$ (248)	$ 364
Guaranteed Minimum Income Benefit | Variable Annuity [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative, Gain (Loss) on Derivative, Net		25
Guaranteed Minimum Income Benefit | Variable Annuity [Member] | Measurement Input, Withdrawal Rate [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative, Gain (Loss) on Derivative, Net		91
Guaranteed Minimum Income Benefit | Variable Annuity [Member] | Measurement Input, Mortality Rate [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative, Gain (Loss) on Derivative, Net		$ 11

[1] Excludes foreign exchange gains (losses) related to GLB.